The study of humoral response of mice to malaria antigens was continued. The work was extended to include analyses of Plasmodium chabaudi infections in addition to P. yoelii. During the year the antigenic cross-reactivity between P. chabaudi and P. yoelii and the humoral responses to the cross-reactive antigens were compared. Cross reactivity at the antibody level was found to be extensive. Further, the antibody response to the cross reactive antigens in the two infections differed with regard to isotype distribution. It was also found that cross reactive antigens can be present on molecules of different size in the two species. In order to examine T cell regulation and control of malaria specific antibody responses during infection, experiments were initiated to establish conditions for the in vitro generation of such antibody responses T cell lines are being developed by the use of hybridoma techniques and continuous in vitro antigen stimulation.